The Problem with Plastics

Male Babies Less MaleOne focus of Zoeller’s research is
how thyroid hormone controls what are called cell fate specifications.
“Undifferentiated cells in the fetal brain have to make decisions about what
they want to be when they grow up. Thyroid hormone helps them make the right
choice,” says Zoeller. “But interfere with the thyroid signal and cells start
to make the wrong decision. That’s irrevocable.”

In animal studies with rats, Zoeller
has shown that low levels of BPA are quite capable of disrupting fetal brain
development, a situation that could lead to “a mosaic of effects,” which he’s
currently attempting to document. And he’s hardly alone in demonstrating BPA’s
ability to interfere with hormone signaling in animal experiments.

Yale School of Medicine
reproductive biologist Hugh Taylor studies what are known as HOX genes,
particularly a suite of them essential for normal uterine development and
fertility. In an ongoing series of investigations, Taylor has exposed pregnant
mice and their fetuses to DES and BPA and gotten similar results: females whose
reproductive systems will not function correctly when they reach adulthood.
“There’s a crucial, vulnerable time period during development,” says Taylor.
“These endocrine disruptors change the fine tuning of the entire program, and
then the effects are locked in for life.”

Phthalates seem to work in a
similar manner, except they target the male set of hormones known as androgens.
“The default developmental plan is actually female,” says Shanna Swan, an
epidemiolo-gist at the University of Rochester School of Medicine and
Dentistry. “The movement toward becoming male is controlled by testosterone
during what we call the fetal programming window. Phthalates, like DEHP, can
compromise the whole cascade toward masculinization.”

In “Environmental Phthalate
Exposure in Relation to Reproductive Outcomes and Other Health Endpoints in
Humans,” a paper published last year in Environmental Research, Swan showed
that male babies born to mothers with relatively high concentrations of several
phthalates in urine samples were, in fact, less male, according to a measure
long used to gauge sexual dimorphism in rodents but only recently used for
humans. This standard is called the anogenital distance, and it turns out that
the distance in females is normally about half that of males. However, in
Swan’s study, which builds on groundbreaking work that she and her team
published in Environmental Health Perspectives in 2005 and 2006, the greater the concentration of phthalates in the
mothers, the shorter the anogenital distance in their male offspring. Girls, as
was predicted from rodent data, were not affected—by this measure, at least.
The more phthalate-exposed boys also had narrower penises, compared to male
infants whose mothers had lower levels of phthalates, and a greater propensity
to have undescended testicles. It’s too early to tell whether these infants
will also have, later in life, a lower sperm count, a higher incidence of
testicular cancer and other hallmarks of what some researchers term “the
phthalate syndrome.”

Swan admits that we can’t yet know
what the long-lasting impact of exposure, if any, will be on these, or any
other, boys. But she cautions against complacency. “So far, when we’ve made
predictions from rodent studies, they’ve been borne out in humans,” she says.
“And the prediction from rodent studies is that exposure does matter—and should
affect male sperm count and fertility.”

In the mid-1980s, British
epidemiologist David Barker proposed that the pattern of heart disease he was
seeing in England actually had its roots in the womb. However, the problem was
not simply bad genes; rather, it was the environment in which the fetus
developed and the mother’s diet, in particular.

The “fetal origins of adult
disease” hypothesis was initially dismissed as ridiculous, but there’s growing
evidence to support it, says Soto, a Tufts University developmental biologist
and one of the pioneers in studying the health effects of EDCs. “Many of the
bad health trends we’re now seeing, from infertility to cancer, can be
correlated with early exposure to BPA and other endocrine disruptors at levels
that fetuses and infants experience every day,” says Soto.

Correlation, of course, does not
imply causation—you learn that in statistics 101. But sometimes the public and
their congressional representatives don’t make that distinction, especially
when they see an increasing number of studies that seem to explain the pattern
of many of the disturbing disease trends of the 21st century.

Steps You Can Take to Avoid Toxic Chemicals

In his book, Green Intelligence:
Creating Environments that Protect Human Health, John Wargo details many of the legal reforms that, if implemented,
could minimize exposure to manmade toxins. But, he warns, “Progress on these
initiatives … is likely to be incremental.” In the interim, he writes, “there
are ways you can reduce your personal exposure to some dangers by strategically
changing what you buy, how you use it and how you live your daily life.”

Wargo offers the following advice
to minimize exposure to endocrine-disrupting plastics:

• Breastfeed your babies.

• Eat low on the food chain and include many fresh fruits
and vegetables.

• Purchase basic and raw organic foods rather than those
that are processed and include multiple ingredients.

• Try limiting your food purchases to items with fewer than
five ingredients. If you cannot pronounce any ingredient, or do not understand
it, avoid it.

• Avoid bottled water and remember that urban supplies are
the best-tested sources of drinking water in the nation.

• Avoid using hot water from the tap for cooking or
drinking.

• Let cold water run for several minutes in the morning
before consuming it.

• Limit the amount of carpet used in your home, because it
harbors chemical residues.

• Minimize use of air fresheners, fragrances and
deodorizers.

• Pregnant women and young children should avoid exposure to
home renovation and construction areas.

• Use nontoxic toys and art supplies, such
as those certified by the Art and Creative Materials Institute.